It is well known to provide a three port, two position spool valve movable in a cage for supplying and exhausting fluid to and from an outlet port as shown in U.S. Pat. Nos. 3,921,660 and 4,011,892, and as illustrated on page 142 in the 1980-1981 General Catalog of Koomey, Inc. Such valves are useful in subsea pods for controlling blowout preventors such as shown in U.S. Pat. Nos. 3,957,079 and 3,817,281.
The present invention is directed to various improvements in such a valve by having (1) a spool valve element which is more fully guided, (2) a cage having a reduction in fluid chambers for reducing flow restrictions, (3) a cage having transversely slotted flow passages for providing full flow passages with a minimum of spool travel, (4) a dash pot between the spool and the cage for cushioning the operation of the spool, (5) a valve structure which provides a metal-to-metal stackup of the valve assembly for correctly loading of the valve seats, (6) a structure which allows the preassembly of the complete valve before installation, (7) a structure which has only one seal which is required to pass an intersecting bore in a valve pocket for decreasing the chances of cutting the seal, (8) a control stem to spool connection that is external to the spool for easier connection, (9) a split ring retainer between a spring plate and the valve stem that is locked into a captive groove, (10) a pilot seal chamber which is filled with a protective fluid pressure compensated from the surrounding environment by a flexible membrane and includes a relief vent, and (11) a pod seal carrier, either of a compression type or a pressure energized type, for use in place of conventional pod seals.